Background : Ginseng (Panax ginseng C.A. Meyer) is one of the most important medicinal plants in Korea, but its yields are often reduced by a variety of root pathogens. The root rot of ginseng is a destructive soil-borne disease caused by Cylindrocarpon destructans (teleomorph: Ilyonectria radicicola). Methods and Results : Ilyonectria radicicola and its Cylindrocarpon-like anamorph represent a species complex that is commonly associated with root rot disease symptoms on virulence. During the course of this study, several species could be distinguished from I. radicicola sensu stricto based on morphological and culture characteristics. As results of investigated culture characteristics, optimal temperature for mycelial growth of isolates were 20℃, and colony pattern and color were slightly different on PDA. Isolates of I. radicicola were analyzed for their genetic relatedness based on several genes and microsatellite region. I. radicicola group was divided into two small groups. Conclusion : Therefore, we were able to confirm pathogenicity and genetic difference between the isolates in each of the groups of the pathogen. Among these isolates, 21.5% were classified as highly virulent and 78.5% were weakly virulent. *(Corresponding

Background : Ginseng (Panax ginseng C.A. Meyer) is one of the most important medicinal plants in Korea, but its yields are often reduced by a variety of root pathogens. The root rot of ginseng is a destructive soil-borne disease caused by Cylindrocarpon destructans (teleomorph: Ilyonectria radicicola). To monitor contamination with C. destructans in ginseng harvested in 2015 were sampled from 57 different growing fields. The spore number of C. destructans was quantified by use of a specific primers and selective media (radicicol) in soils of ginseng fields. Methods and Results : The ginseng samples were surface-sterilized and placed on potato dextrose agar plates for 7 day incubation at 20℃. Emerging fungal colonies were counted primarily based on colony and conidia morphology. Further species level identification was confirmed by ITS rDNA sequencing. For quantification of the soil-borne C. destructans, the genomic DNA was extracted from the soil using a NucleoSpin soil kit (MN, Germany). Density of C. destructans was determined by species specific real time PCR (qPCR). The qPCR was completed by running a melting curve analysis. Conclusion : The C. destructans associated with root rot disease of ginseng were detected in more than 60% in pyeongtaek-1, pochenon-1, jecheon-1, chungju-1 and jinan-4. As results of the study, the correlation between pathogen density and identification clearly clarified in the soil.